Hillary Clinton has relaunched her campaign on Roosevelt Island with a 4,687-word speech. But it's not clear whether she and her husband, Bill Clinton, can win four presidential elections as Franklin D. Roosevelt did. Negative news for Clinton's prospects comes in the latest Quinnipiac polls in the key mega-states of Florida, Ohio and Pennsylvania. In each of them, she leads or ties Republican opponents, though in many cases not by statistically significant margins. But she also is running under 50 percent of the vote in every pairing, averaging 47 percent against six different Republicans in Florida, 44 percent against seven...